The present invention concerns a process for repairing plastic coatings of metal pipes, that allows the repairs to be made in a very short time.
Metal pipes, usually made of steel, coated with plastic material, are widely used for building pipelines conveying fluid materials, such as oil, natural gas, or water, even for a long distance.
Said pipelines must be able to withstand the most diverse environmental conditions, and, in certain cases, the high temperatures that are maintained in the proximity of pumping stations, for example, or that may be typical of certain fluids extracted from the subsoil.
In order to avoid weak points along the line it is necessary, therefore, that the damaged or removed segments of the plastic coating (where the pipes are welded together, for example) be repaired in such a way that the mechanical properties are as homogeneous as possible with the ones of the original coating.
As a response to said needs there are materials and methods known in the art which allow one to reach said objective with satisfactory results.
However, when the damaged portion of the coatings is quite extensive (for example when the coating has been removed in order to weld the pipes), one needs complicated repairing techniques requiring long times, and sophisticated and costly apparatus, such as induction ovens.
Now has been perfected a particularly fast and efficient repair method which allows one to limit the use of the induction oven to the heating phase preceding the application of the primer, and to carry out the other heating phases by using a flame shielded by inert gas (such as nitrogen, for example).
Said process is particularly suited for repairing polyolefin coatings, preferably polypropylene and/or polyethylene coatings.